For the limoncello: Pour the entire bottle of vodka into a glass jar. Add lemon zest from all 10 lemons. I prefer to use a microplane zester, to ensure I don't get any of the white pith. If you have a peeler that works well and it allows you to only peel off the thin outer yellow skin without any pith, go ahead and use that. If the white pith is added to the vodka, your limoncello will likely have a bitter flavor.

Seal the jar tightly with a lid and set it in a cool, dark place for 1 week and up to 1 month. The length of steeping time will depend on the oil content of your lemons and the proof of your liquor. The first week will extract the most flavor from the lemon zest, so give the mixture a gentle swirl every couple days during that time. After 1 week, swirl and taste-test every couple days. When it has a bright and sunshiny, tangy lemon flavor, it’s ready for the next step.

Line a colander with a double layer of cheesecloth and place it over a bowl. Pour vodka mixture through the cheesecloth. Gather up the cheesecloth and use a spatula or the back of a wooden spoon to press on the cheesecloth and extract every last bit of lemon flavor into your limoncello. Discard cheesecloth full of lemon zest.

For the simple syrup: Stir together water and sugar in a medium saucepan over medium-high heat, and bring it to a boil. Whisk rapidly until the sugar dissolves completely. Remove from heat and allow to cool completely.

To create the limoncello: Add 1 cup of the cooled simple syrup to the lemony vodka mixture. Then give it a taste test. Add more simple syrup if you'd like it sweeter, until it’s flavored to your liking. You can make it as sweet as you like. You now have limoncello!

Pour the finished lemon liqueur into a freezer-safe bottle that has a tight-fitting cap. Place in the refrigerator or freezer. I like to keep mine in the freezer, for an ultra chilled cordial at a moment’s notice – plus it’ll keep longer. The high alcohol content will keep it from freezing (another plus to using 100-proof alcohol or higher). If you store yours in the fridge, move it to the freezer an hour before serving to bump up the chill.

Store remaining simple syrup in the refrigerator, in a container with a tight lid. When trying your chilled limoncello for the first time, feel free to add more simple syrup if you'd like it sweeter. I added what I thought should be the minimum amount of simple syrup, with additional simple syrup available if needed. Once you've added the desired amount of simple syrup, use any remaining simple syrup for lemonades, cocktails, teas, and coffee drinks.